X-ray studies of terpenoids. Part III. A redetermination of the crystal structure of (+)-3-bromocamphor: the absolute configuration of (+)-camphor

Abstract

Crystals of (+)-3-bromocamphor, C₁₀H₁₅OBr, are monoclinic, space group P2₁, with a= 7·36 (1), b= 7·59 (1), c= 9·12 (1)Å, β= 94·1 (2)°, and Z= 2. The crystal structure has been accurately redetermined by use of three-dimensional X-ray diffraction data (R= 0·071 for 836 visually-estimated reflection intensities), in order to establish unambiguously the absolute configuration of the key monoterpene (+)-camphor. This determination has confirmed earlier, non-rigorous assignments using both chemical and X-ray techniques. The importance of this configurational assignment in the stereochemical correlation of the monoterpenes is discussed. The geometry of the norbornane skeleton is compared with data from other X-ray studies.